<!DOCTYPE html>
<title>CSS Position Test: overlay transition with ::backdrop</title>
<link rel="help" href="https://drafts.csswg.org/css-position-4/#overlay">
<link rel="match" href="green-ref.html">
<link rel="author" href="mailto:jarhar@chromium.org">
<style>
  [popover] {
    display: block;
    visibility: hidden;
    transition: overlay 60s step-end;
    transition-behavior: allow-discrete;
  }
  [popover]::backdrop {
    visibility: visible;
    background-color: green;
  }
</style>
<div popover id="foo"></div>
<script>
  foo.showPopover();
  foo.hidePopover();
</script>
